Irisin was first identified in muscle cells. We detected irisin immunoreactivity in various organs of the crested porcupine (Hystrix cristata). In the epidermis, irisin immunoreactivity was localized mainly in stratum basale, stratum spinosum and stratum granulosum layers; immunoreactivity was not observed in the stratum corneum. In the dermis, irisin was found in the external and internal root sheath, cortex and medulla of hair follicles, and in sebaceous glands. Irisin immunoreactivity was found in the neural retina and skeletal muscle fibers associated with the eye. The pineal and thyroid glands also exhibited irisin immunoreactivity.
Irisin was first identified in skeletal muscle cells. It is an exercise protein that is secreted into the circulation; it causes conversion of white adipose tissue to brown adipose tissue. We investigated irisin immunoreactivity in mole rat (Spalax leucodon) tissues. We examined cerebellum, pituitary, heart, liver, pancreas, spleen, uterus, kidney and striated muscle in female adult mole rats. Tissues were processed, embedded in paraffin, sectioned at 5 μm and stained immunohistochemically for irisin. Irisin immunostaining was detected in the cytoplasm of stained cells; the cytoplasm of Purkinje cells was unstained. We found that irisin may be synthesized in many tissues. The function of locally synthesized irisin currently is unknown.
A 55-year-old female presented with elastofibroma of the thigh. On presentation, she complained of a palpable, painful mass on the anterolateral right thigh that had been present for one year. She had a history of surgery for a right femur fracture. On MRI, a soft-tissue mass was seen in the vastus intermedius muscle, as a heterogeneous lesion with streaky fatty and fibrous components. The fibrous component was isointense to the muscle, and the fatty component had a high signal on both T1-and T2-weighted images. Histopathological analysis after biopsy established the diagnosis of elastofibroma.
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